The 20th Century is often said to be the bloodiest century in recorded history. In addition to its wars, the century witnessed many grave and widespread human rights abuses. But what stands out in historical accounts of those abuses, perhaps even more than the cruelty of their perpetration, is the inaction of bystanders. Why do people and their governments repeatedly fail to react to genocide and other mass scale human rights violations?

A chapter in Eldar Shafir’s edited volume, The Behavioral Foundations of Policy, forthcoming from the Russell Sage Foundation and Princeton University Press. Posted on SSRN in advance of publication with kind permission from Princeton University Press.